Unity External sources

Question

I get the error Wwise: Cannot open file: SeedDrop.wem when I call PostEvent from external sources.

AkExternalSourceInfoArray source = new AkExternalSourceInfoArray(1);
source[0].iExternalSrcCookie = AkSoundEngine.GetIDFromString(_cookie);
source[0].szFile = @"SeedDrop.wem";
source[0].idCodec = AkSoundEngine.AKCODECID_PCM;
AkSoundEngine.PostEvent(_subtitlesWwiseEvent.Id, gameObject, 0, null, null, 1, source);

I call like this, my banks are made, and the sources in the Wise application are pulled up. 
Path to SeedDrop.wem is D:\game\WwiseProject\GeneratedSoundBanks\Windows